This section provides background information to facilitate a better understanding of the various aspects of the invention. It should be understood that the statements in this section of this document are to be read in this light and not as admission of prior art.
The concept of separating oleophilic matter from hydrophilic matter goes back as far as the year 425 BC where Herodotus, a Greek historian and traveler, observed maidens on an island drawing cold bitumen coated feathers through wet beach sand to collect gold dust by oleophilic adhesion. Many centuries later, in 1860, William Hanes separated oleophilic sulfide from hydrophilic gangue material using froth flotation of oil wetted sulfide. In 1920 Karl Clark invented a bitumen froth flotation process to separate bitumen droplets from mined oil sand by using air bubbles to cause bitumen to float as a froth.
Currently commercial separation of mined oil sand slurries is done by the Clark froth flotation process invented in 1920 by Dr. Karl Clark at the Alberta Research Council and progressively improved thereafter to increase separation efficiency from an optimum 90% bitumen recovery to the current 95% bitumen recovery from water based slurries of mined oil sand ore that contain at least 10% bitumen. Process temperature of the slurry feed, as a result of continued froth flotation research, was reduced from 95° C. to 50° C. to conserve energy. However, the current commercial process still requires 6 hours (360 minutes) of separation time to capture by flotation about 95% of the bitumen contained in the mined ore used to form the slurry.
Froth flotation requires the addition of a caustic chemical to react with components in the oils and feed to form a detergent or dispersant to yield a water based slurry containing suspended small droplets or films of bitumen in the water based slurry. These droplets or films attach to small air bubbles introduced into the slurry and rise to the top of separation vessels to yield an aerated bitumen froth product that is skimmed off the vessel's top. The process requires very large flotation vessels and several recycle loops to optimize bitumen product quality and recovery. After that, the bitumen froth is deaerated and processed by dilution centrifuging or solvent extraction to yield an acceptable bitumen product for further refining and upgrading to synthetic crude oil and/oil refinery products.
Froth flotation leaves behind long duration tailings ponds that contain fluid fine tailings (FFT) of water, suspended fines and between 5% and 10% of the bitumen contained in an oil sand slurry. The FFT must be impounded indefinitely in sealed tailings ponds so as to prevent leakage into the adjacent groundwater, rivers or lakes. It is estimated that the current mined oils and tailings ponds contain in excess of one billion barrels of discarded bitumen which, according to pilot plant studies, are easily recovered by oleophilic separation, taking less than 10 minutes of process residence time for the separation. Microbial action in those ponds result in the generation of methane release to the environment.
In 1975 the present inventor invented the concept of using an oleophilic sieve to separate bitumen from a feed of mined oil sand slurried in water. In his process, the feed passed through an oleophilic sieve which captures bitumen phase on sieve surfaces and allows aqueous phase and hydrophilic minerals particles to pass through sieve apertures. Since then he has continued to perfect that previously untried concept. Oleophilic separation was developed to replace bitumen froth flotation as well as minerals froth flotation.